(a) Field of the Invention
The present invention relates to a tool with improved impact and torque capabilities and having ergonomic handle. The tool may be a screwdriver, chisel, or the like. For example, the tool shank has a hex shaped portion integral to the two part ergonomic handle, which, with the dual molded handle composition, provides these increased tool capabilities. The ergonomic handle has a polypropylene core molded about the shank and a thermoplastic rubber cushion grip molded about the polypropylene core.
(b) Description Of the Prior Art
It is known in the art to provide a screwdriver shank having wings, or flattened portions, on the shank portion included in the handle of the screwdriver. The wings function when the screwdriver handle is being rotated or torqued to transfer the torquing forces to the shank and to prevent the shank from turning within the handle.
If the end of the tool handle is hit by, for example, dropping a screwdriver handle down onto a hard surface or hitting a chisel on the handle, the shank portion extending into the handle can cause the handle to fail, ruining the tool. One method of overcoming this is to extend the shank through the handle. Another method is to provide a flared out bolster portion of the shank at the handle base toward the tool end, such as taught by Forsberg in U.S. Pat. No. 3,302,673. However, experience has shown that, while the flared out bolster portion absorbs some of the forces, the handle can still fail.
While Forsberg teaches a flared out bolster, it is also known to shape the bolster at the tool base of the screwdriver handle, for example in a hexagonal shape, so that an external tool, such as a wrench, can be used to assist the hand in torquing or turning the screwdriver.
To increase torquing capabilities, screwdrivers having a handle, for example of cellulose plastic, are known having a sleeve thereover. Coyle U.S. Pat. No. 2,871,899, et al., teaches such a sleeve 15 of resilient rubber-like material having a durometer reading of between 40 and 90 Shore A. More particularly, a sleeve of neoprene rubber, having a durometer reading of between 55 and 70 Shore A, is taught. Coyle teaches that the sleeve can be held in place on the handle simply by friction, or it may be adhesively cemented thereto. To aid in torquing, Coyle also teaches mechanical interlocking of the sleeve and handle by having mating grooves and ribs on the inside of the sleeve and outside of the handle, respectively. Stowell U.S. Pat. No. 3,189,069, teaches another handle body having a fluted grip 24 frictionally received thereover.
Older known screwdriver shanks, before handles were attached thereto and, thus, before shank wings, are known having a head on the end opposite the tool end. Hadfield U.S. Pat. No. 2,609,851, to teaches a small screwdriver having such a head 16 on shank 14, which has been molded into a handle 15. This head 16 functions as the currently used shank wings, in that it helps prevent the shank 14 from turning in handle 15.